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COSEWIC assessment and update status report on the Bluehearts in Canada

Technical Summary

Distribution

Extent of occurrence:< 5 km2
Area of occupancy:< 1 km2 (1.4 ha)


Population Information

Total number of individuals in the Canadian population:553 in 1997 from 6 of 8 sites
Number of mature reproducing individuals in the Canadian population:unknown
Generation time:one year
Total population trend:unknown
Rate of decline (if appropriate) for total population: 
Number of known populations:a total of about 8 sites with several additional subpopulations have been recorded along a 10 km stretch of Lake Huron shoreline habitat and one historic site (1914) on Squirrel Island
Is the total population fragmented?Yes
number of individuals in smallest population:0 (based on fluctuating population sizes)
number of individuals in largest population:1971 in 1994
number of extant sites:6
number of historic sites from which species has been extirpated:at least 3
Does the species undergo fluctuations in numbers?Yes
If yes, what is the maximum number?2182 in 1981 at 7 sites
minimum number?553 in 1997 at 6 sites
Are these fluctuations greater than one order of magnitude?possibly


Limiting Factors and Threats

High water levels, cottage development and recreational activities.


Rescue Potential

Does the species exist outside Canada?Yes
Is immigration known or possible?Possible but not very probable
Would individuals from the nearest foreign population be adapted to survive in Canada?unknown (disturbance factors are different at the nearest US sites)
Would individuals from the nearest foreign population be adapted to survive in Canada?probably